دانلود رایگان مقاله انگلیسی بررسی پتانسیل مربوط به رویداد اثر همگرایی معنایی در هنگام رمزگذاری اپیزودیک در بیماران اسکیزوفرنی - هینداوی 2018

The objective of this electrophysiological study was to investigate the processing of semantic coherence during encoding in relation to episodic memory processes promoted at test, in schizophrenia patients, by using the N400 paradigm. Eighteen schizophrenia patients and 15 healthy participants undertook a recognition memory task. The stimuli consisted of pairs of words either semantically related or unrelated to a given category name (context). During encoding, both groups exhibited an N400 external semantic coherence effect. Healthy controls also showed an N400 internal semantic coherence effect, but this effect was not present in patients. At test, related stimuli were accompanied by an FN400 old/new effect in both groups and by a parietal old/new effect in the control group alone. In the patient group, external semantic coherence effect was associated with FN400, while, in the control group, it was correlated to the parietal old/new effect. Our results indicate that schizophrenia patients can process the contextual information at encoding to enhance familiarity process for related stimuli at test. Therefore, cognitive rehabilitation therapies targeting the implementation of semantic encoding strategies can mobilize familiarity which in turn can overcome the recollection deficit, promoting successful episodic memory performance in schizophrenia patients.

4. Discussion

The aim of this study was to investigate the encoding and retrieval phases in an associative recognition memory task in schizophrenia patients by the means of ERPs. We manipulated the semantic coherence of to be learned stimuli and expected semantically related word pairs to induce higher recognition rates compared to unrelated word pairs in both healthy controls and schizophrenia patients. We hypothesized that, during encoding, the electrophysiological data obtained in schizophrenia patients would indicate an N400 external coherence but a lack of an N400 internal coherence effect between the related and unrelated conditions. We also believed that this lack of N400 internal coherence effect in schizophrenia patients would be accompanied by a lack of parietal old/new effect during retrieval. However, we thought there would be an early mid-frontal old/new effect for semantically related stimuli in the patient group. As expected, the behavioral results showed an increase of correct response rates for semantically related stimuli in comparison to semantically unrelated stimuli in both groups. The electrophysiological data indicated that, as hypothesized, healthy controls, but not schizophrenia patients, presented the N400 internal coherence effect between the related and unrelated conditions during encoding, whereas the N400 external coherence effect was present in both groups. Test phase data showed an early mid-frontal negativity for new word pairs compared to old word pairs, accompanied by a late positivity for new word pairs compared to old ones, for the related condition in healthy controls alone, while, in schizophrenia patients, only early mid-frontal old/new effect was observed for related stimuli.